This video suggests that the earthquake that shook north east Japan May 3 2015 was responsible fro the emissions soon visible at Daiichi after the shaking stopped:
I strongly recommend watching the video.
I was not watching the cams during the earthquake but noticed that the emissions seemed unusually thick when I started watching the cams about 10 hours later. I also documented the very large boat in the harbor http://majiasblog.blogspot.com/2015/05/unceassing-emissions.html
I created a file of screenshots because the fog didn't look right the next day:
I've been having trouble getting TEPCO cams 1 and 4 to load today.
In this recent video, Prof. Koide states repeatedly that the melted fuel requires continuous cooling to avoid escalation of reactions: Hiroaki Koide: "The Trouble with Nuclear Power"